Ok I see a lot of you guys are pushing with your support hand, I tend to... Not do that.
I was taught to do nothing other than support the gun with my non firing hand I don't really "stretch the gun" I pull the gun into my shoulder with my firing hand.
With varied pressure depending on what I am doing.
That being said I'll be at the range shooting 308 and 300wm in sporter weight rifles day after tomorrow so I will play around with the pulling with my support hand.